1. Field of the Invention
The invention relates to an illumination device and an image display apparatus, and more particularly, to an illumination device used as a light source of a projection type image display apparatus such as a projector, and an image display apparatus including the illumination device.
2. Description of the Related Art
In recent years, in regard to watching movies at home, a presentation at a meeting, or the like, the opportunities to use a projection-type image display apparatus, such as a projector, have been increasing. In such a projector, as a light source, for example, a discharge type lamp, such as a mercury lamp, having high brightness is generally used. In addition, with the recent progresses in the development techniques for solid-state light emitting devices (for example, semiconductor lasers, light emitting diodes, or the like), there has been also suggested a projector using the solid-state light emitting device (for example, see JP-A-2009-277516).
The projector disclosed in JP-A-2009-277516 is a DLP (Digital Light Processing: registered trademark) type projector. In such a type of projector, images are displayed in full color through a time division display of approximately several thousand times per second for the different colors.
The projector disclosed in P-A-2009-277516 has a light source device that includes a light emitting diode (excitation light source) that emits blue light (excitation light), a transparent substrate provided at an emission side of the excitation light, and a motor that rotates the transparent substrate in a plane orthogonal to an emission direction of the excitation light.
In the light source device disclosed in JP-A-2009-277516, a red fluorescent layer that emits red light by the irradiation of the excitation light, a green fluorescent layer that emits green light by the irradiation of the excitation light, and a region that transmits the excitation light “as is” are formed at different regions on a transparent base. Therefore, in regard to the projector disclosed in JP-A-2009-277516, when the excitation light is emitted to the transparent base rotating with a predetermined number of rotations, the blue light (excitation light), and red light and green light excited by the excitation light are time-divisionally emitted from the light source device.